tips for epoxy filling

[yukon cornelius]

Im almost behind on a fireplace hearth job. I have the slab planed and have some divots the customer wanted filled. I have never done this and I didn't get to do my research beforehand. but I am headed to the shop in a few minutes to clean out the divots and try to fill them. My biggest questions are dry time and when it will be sanding ready for sanding. Any advice is appreciated.

[Den-Den]

I have used epoxy for filling voids many times.  Cure time depends on which epoxy and temperature (very temperature sensitive).  I don't like to use "5 minute" epoxy as it can start setting up too fast.  In larger voids or in the mixing container, it will generate its own heat and go off suddenly.  In small amounts at cold temperatures, it can take a day or two.

[yukon cornelius]

I did it! it was surprisingly easy I thought. it set up rigid fairly quick and now I wait while I sleep to sand it. I was a bit short on one hole so I left it shallow. I will see how it looks tomorrow.

I remembered to late about using a heat gun to release bubbles.

No pictures since I was so pressed for time but I will try to remember in the morning. thanks den!

[Brad_bb]

I use West systems.  It's the only one I've tried.  Tips, your ratio of epoxy to harder should be exact as possible to the Mfg instructions.  I use a fast hardener.  You do have to be careful if you try filling large/deep pockets.  It can generate too much heat and cause cloudiness/bubbles.  Fill large pockets a bit at a time.  You can come back after the first batch has cured and add more.  Make sure to pop the bubbles with a heat gun or a torch.  Just a quick pass over the spot will pop them.  They will often keep forming bubbles for 1/2 hour or more until it's actually set up, so keep an eye on it and pop the bubbles as they come up.  If you leave bubbles and have to add more epoxy, you're going to see the bubble- it won't be clear or homogeneous.  Use high quality masking tape like 3M automotive (green) and really go over it to make sure it's adhered well.  Even after you do some times epoxy will find it's way out under the tape.

[yukon cornelius]

I finished the hearth and the epoxy turned out pretty good! The second filling of the largest hole was milky or cloudy. it was as different package but the smaller holes I touched up were clear. I used the heat gun but I think it might have been a little too much just as Brad said. I was worried but the customer loved it!  Im glad I have it under my belt and now I can refine it a bit on another. thanks for your advice!

[hackberry jake]

I use "table top" epoxy. I found that if I warm up the two parts, I get less bubbles. It is also a good idea to put on a thin layer and let it harden. This will keep the wood from absorbing it all (end grain) and seal off anything that might leak air bubbles into the epoxy.

[low_48]

My favorite epoxy filler is dry used coffee grounds, if you want a dark color. The grounds will give you a slight range of color and doesn't have the plastic look of tinted epoxy.